Pulse oximetry is a technique known in the art for measuring absorbencies in pulsing arterial blood. As one of ordinary skill in the art of pulse oximetry understands, a pulse oximeter may also be used to monitor real time heart rate and arterial oxygen saturation levels.
Pulse oximetry works on the basic concept of light absorption by hemoglobin, the oxygen carrying molecule in red blood cells. Hemoglobin has four oxygen binding sites per molecule. The molecule may absorb a certain amount of light emitted by a pulse oximeter, based on how many of the molecule's oxygen binding sites are bound to an oxygen molecule. The wavelength of unabsorbed light sensed by the pulse oximeter may be used to calculate the amount of oxygen bound per hemoglobin molecule. By taking an overall average of these sites, the percentage of the total blood oxygen saturation is calculated.
To accurately monitor light absorption, certain pulse oximeters must be placed on the body in an area where the skin is thin enough for light to pass through yet has enough vascular tissue to generate an acceptable measurement (e.g., ear lobe or tip of an index finger). Certain other pulse oximeters, however, monitor light absorption by measuring the amount of light reflected from a user's body, as opposed to the amount of light that passes through. Reflective pulse oximeters leverage the fact that hemoglobin molecules reflect certain wavelengths of light based on the number of oxygen-binding sites that are bound to oxygen and, as such, may be placed on the body in areas that have dense capillary beds and/or arteries near the skin surface (e.g., underside of the wrist, chest sternum, forehead, etc.).
Notably, pulse oximetry measurements, whether taken with a “pass-through” pulse oximeter or a “reflective” pulse oximeter, are prone to inaccuracies due to electrical noise introduced by user movement. The effect of motion artifact on the accuracy of a pulse oximetry measurement makes pulse oximetry technology known in the art less than ideal for real time pulse oximetry monitoring in users that are moving, such as athletes, runners, etc. Body movement during a reading may provide inaccurate, misleading, or ineffective data. Therefore, there is a need in the art for a system and method that provides an accurate pulse oximetry reading, as well as other physiological calculations and/or combinations of physiological calculations, when a user is in motion.